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Abstract

Hepatocyte Growth Factor (HGF)–induced Epithelial–Mesenchymal Transition (EMT) is a complex cellular pathway that causes epithelial cell scattering by breaking cell–cell contacts, eliminating apical–basal polarity, and replacing epithelial markers and characteristics with mesenchymal markers. Early EMT events include a brief period of cell spreading, followed by cell compaction and cell–cell contact breaks. A forward chemical genetics drug screen of 50,000 unique compounds measuring HGF–induced cell scattering identified 26 novel EMT inhibitors, including 2 proteolytic inhibitors. Here, we show that B5500–4, one of the EMT inhibitors from the screen, blocks HGF–induced EMT by a predicted blocking of the protease furin, in addition to secondarily blocking Beta–Secretase (BACE).We also show that MMP–12 and MMP–9 are required for HGF–induced EMT to progress. MMP–12 is required for cell contraction, and its inhibition produces a continuous cell spreading phenotype.We also demonstrate that both furin and BACE activity are required for HGF–induced EMT to proceed, but that they are involved in separate pathways. We show that BACE inhibition leads to a failure of cell spreading in early EMT, and that EphA2 is a member of this pathway. We also demonstrate that it is likely BACE2, and not BACE1 that is responsible for early cell spreading. Furin is also required for HGF–induced cell scattering, but does not play a role in the cell spreading process. These findings highlight the importance of proteolytic activity at the earliest stages of HGF–induced EMT.